Greases containing a lithium soap of polymerized 12-hydroxy stearic acid and their method of manufacture



United States Patent GREASES CONTAINING A LITHIUM SOAP OF POLYMERIZED 12-HYDROXY STEARIC ACID AND THEIR METHOD OF NIANUFACTURE t No Drawing. Application February 17, 1951, Serial No. 211,575

3 Claims. (Cl. 252-41) My invention relates to improvements in the manufacture of lithium greases containing the lithium soap of polymerized 12-hydroxy stearic acid. The manufacture of greases containing lithium soaps of l2-hydroxy stearic acid is disclosed in United States Patent No. 2,397,956 to Harold M. Fraser. Superior properties for such lithium greases are described therein including particularly the ability to maintain consistency when mechanically worked. One of the salient features of manufacture is the step of heating the reaction mass, usually including most of the oil, to about 425 F. at which temperature the mass is fluid. Unless this high temperature is attained, the consistency of the grease is low so that excessive proportions of soap are required for a given penetration grease and the appearance and texture of the grease are poor. The manufacturing procedure further involves a controlled cooling rate for the stirred mixture from about 425 F. down to about 225 F.

The high temperature requirement in the manufacture of greases containing lithium soaps of 12-hydroxy stearic acid represents a serious disadvantage from the standpoint of the practical art. The use of conventional grease equipment is not feasible and either special, expensive pressure equipment, or other high temperature equipment is required. Thus many refiners have turned from use of lithium soaps of the more desirable grease making acids to use of lithium soaps of less desirable acids which may be produced within the temperature limits of ordinary grease making kettles, i. e., 250 to 330 F. Surprisingly, however, I have found that a grease containing the lithium soap of polymerized l2-hydroxy stearic acid can be produced in excellent quality, and with soap economy, without exceeding 330 F. By polymerized 12-hydroxy stearic acid, I mean the composition formed by self-reaction or condensation of l2-hydroxy stearic acid. It probably comprises a mixture of some or all of the following substances: the hemilactide, lactide and lactone of 12-hydroxy stearic acid, the trimer of 12- hydroxy stearic acid and longer chain cyclic or linear polymers formed by interesterification or similar condensation, together with some unreacted' 12-hydroxy stearic acid. The polymer may be readily formed by heating 12-hydroxy stearic acid, either alone or in the presence of a trace of mineral acid, to about 150 to 300 F. and holding at this temperature for a few hours. The longer the heating, up to equilibrium, the more complete is the condensation.

I have found that a soap of a lithium base and polymerized 12-hydroxy stearic acid may be formed by mixing the lithium base with the acid, preferably in the presence of oil, and heating the agitated mixture until substantially all of the water has been removed (around 220 to 250 F.). Heating then is continued in the presence of oil until the temperature of the agitated soap-oil mixture has reached a temperature of 300 to 330 F. Usually, the polymerized IZ-hydroxy stearic acid is charged to the kettle first and melted, which occurs at about 170 to 190 F. Starting oil may be omitted, but saponification in the presence of oil facilitates the finishing stages of formulation. Advantageously, starting oil is used in the ratio of from about 0.5/1 to 4/1 oil to fatty acid. Higher proportions of oil to polymerized 12-hydroxy stearic acid up to all of the oil to be present in the finished grease may be used but flexibility in finishing different batches to the same penetration or consistency is reduced.

When the kettle charge has been brought to 170 to 200 F., the calculated amount of the lithium base for saponification of the 12-hydroxy stearic acid is added. Advantageously, the lithium base is added as a boiling water solution of lithium hydroxide monohydrate in about 3/1 to 8/1 ratio of water to lithium hydroxide monohydrate. Other lithium bases may be used, e. g. anhydrous lithium hydroxide, lithium hydroxide monohydrate or lithium carbonate. Neutralization proceeds instantly followed by saponification. Thorough mixing with the addition of heat, e. g. to p. s. i. steam in the kettle jacket, is continued until substantially all the water has been removed, i. e. about 220 to 250 F., and the soap-oil mixture has reached a temperature of 300 to 330 F.

The soap-oil mixture is cooled by addition of the remainder of the oil if all the oil is not added in the kettle charge. Circulation of cooling water in the kettle jacket of course may be employed to cool the mixture or to supplement the internal cooling by oil addition. Various inhibitors may be added when the grease is cooled below 200 F. The grease may be drawn as a finished product directly from the kettle but preferably is mechanically processed as in a colloid mill or roll mill and then is deaerated to give a smoother product of somewhat better physical properties and somewhat lower soap content.

The proportion of soap in the oil is controlled by checking hardness and penetration of control samples during the finishing operation and adjustment of these properties by oil addition. I have found that the use of polymerized 12-hydroxy stearic acid as a starting material in the manufacture of lithium greases at maximum temperatures of 300 to 330 F. results in halving the amount of soap required for a typical #2 grease compared to the use of ordinary 12-hydroxy stearic acid while eliminating the conventional high temperature processing step.

Polymerized 12-hydroxy stearic acid may be obtained as such on the commercial market. It also may be produced readily from 12-hydroxy stearic acid by action of a very small amount of a mineral acid, e. g. sulfuric, on the melted material and, if desired, it may be formed in situ in the grease kettle as a preliminary step to the formation of. the lithium soap of the polymerized 12-hydr0xy stearic acid in the grease manufacture according to my invention.

Tabulated below are the composition analysis and tests on three lithium greases which illustrate the special value in using polymerized l2-hydroxy stearic acid as a starting material according to my invention. Grease No. l and Grease No. 2 are lithium greases prepared from polymerized l2-hydroxy stearic acid in two different check )reparations which show that a uniform product may be readily prepared. Grease No. 3 represents a lithium grease prepared from ordinary l2-hydroxy stearic acid. All of the compositions were made at a maximum formulation temperature below 330 F. It will be noted that Grease No. 3 required 25 per cent lithium soap or approximately twice the amount of soap required in Grease No. 1 and Grease No. 2 for greases of approximately equivalent penetration. The cost differential represented makes composition 3 wholly non-competitive so that some processing expedient such as the high temperature technique described in Fraser Patent 2,397,956 is required. However, the high temperature processing technique in turn suffers cost disadvantages due to greater capital investment costs for pressure equipment and higher operating cost caused by the necessity of heating to higher temperatures.

The physical and certain chemical tests on the components of the three illustrative greases are tabulated below in Table I.

3 4 TABLE I kettle contents cooled to below 200 F., the oxidation inhibitors were added (22 parts of Hyamine B [2,6-(di-. Grease N 1 2 3 methylaminomethyl-)4-octyl-phenol] and 22 parts of I octylated arylalkylated diphenyl amine) and thoroughly P1 d P] d mixed. The grease was then cooled to 120 F. and 0 meme ymem? 12 Hy p y processed through a colloid mill and vacuum deaerator at Acid 2 y m y 12 yd y steam Stearic Stearic 1.5 pounds per minute and 0.005 mill clearance.

7 6 8 Grease N0. 2

5.8 7 .8 1 1.0 178.0 193.1 186.1 10 Grease No. 2 was prepared in exactly the same way 3-? as Grease No. 1 except that polymerized 12-hydroxy stearic acid from a difierent batch of acids was used. The second batch had a slightly higher saponification Lithium Hydroxide Monohydrate (same for all three greases?) number; hence, slightly more lithium hydroxide was re- I i 0 P 3- 15 quired. Also, the ratio of starting oil to the acid was 12 s Percen changed to 4/1 (0.5/1 iii first grease) so that 600 parts 11 for ant tee greases) of acid and 2400 parts of mineral oil were added to the 750 SUS at 100 1?. Coastal e l kettle. No inhibitors were added to the grease.

percent v01unie oi 1'20 SUS at 210 F. Mid-Continent-Solvent Grease N0, 3 Refined Residuuin I)G1'CelltVOllll!l0 43 Tests: I on Grease No. 3 was prepared in exactly the same way gf fi f API 22% as Grease No. 1 except that ordinary 12-hydroxy stearic i: '0 acid was used as the acid. Not nearly so much finishing Viscosity, SUS: oil could be added because of the poor yield. Only onefi 8: 25 half the percentage of oxidation inhibitors were in- P of 1' eluded. 031%? NPA 5 Attached Table II lists the kettle charge, finishing ma- CaFbOH Residue. Percent 8- terials, compositions and physical properties for each of Acld the three greases.

TABLE II Grease No 1 2 3 Kettle Charge:

Fatty Acid, parts Mineral Oil, parts Lithium Hydroxide Monohydrate, parts Finishing Materials:

Mineral Oil, parts Octylated arylalkylated Diphenyl Amine,

parts.

Hyamine 13, parts Grease Composition:

Lithium Soap, percent Wt AlglG 10 Bleed Test, Percent Oil Separa- 1011. Boiling Water Resistance Norma-Hofliman Oxidation Test, p. s. i.

drop in 500 hours.

Pass Good.

Excellent. 11.0.

Excellent The formulation procedure for the three greases follows:

Grease N 0. 1

Six hundred parts of polymerized 12-hydroxy stearic acid and three hundred parts of mineral oil were charged to a steam heated grease kettle. These components were mixed thoroughly by stirring and heating to 180 F. (above melting point of the acid). A boiling solution of lithium hydroxide (5 parts by weight water and 1 part by weight lithium hydroxide monohydrate) was added to the oil-fatty acid system and the entire contents were stirred at 180 to 200 F. for thirty minutes. The temperaturewas held below 200 F. to keep the water present and thus aid saponification. At the end of thirty minutes, a full head of 120 p. s. i. steam was put on the kettle jacket to raise the temperature and drive oil as much water as possible. The temperature remained at about 240 F. until most of the water had been evaporated then rose rapidly to 325 F. The dehydrated soap base was then held at 325 F. for one hour during which time about 500 parts of oil were added in small increments. The remainder of the finishing oil (3000 parts) was added just as rapidly as it could be mixed into the soap base (required about one hour). Cooling water was put on the kettle at the start of finishing oil addition to facilitate cooling.

When all of the finishing oil had been added and the I claim:

1. The method for manufacturing lithium greases which comprises heating at a temperature of about 170 to 250 F. a reaction mixture consisting essentially of a lubricating mineral oil, a lithium base and polymerized 12-hydroxy stearic acid, the polymerized 12-hydroxy stearic acid being prepared by heating 12-hydroxy stearic acid to about to 300 F. for a period of time willcient to reach substantial equilibrium and the lithium base being present in said reaction mixture in amount sufficient to saponify the polymerized 12-hydroxy stearic acid, adding to the reaction mixture lubricating mineral oil in amount not exceeding the amount to which the lithium soap present will impart grease consistency to the total oil, and heating the reaction mixture to a temperature of about 300 to 330 F.

2. The method for manufacturing lithium greases which comprises heating at a temperature of about to 200 F. a reaction mixture consisting essentially of a lubricating mineral oil, a lithium base and polymerized 12-hydroxy stearic acid to form the lithium soap of the polymerized 12-hydroxy stearic acid in amount sufficient to impart grease consistency to the oil, the polymerized l2-hydroxy stearic acid being prepared by heating l2- hydroxy stearic acid to about 150 to 300 F. fora period of time sufiicient to reach substantial equilibrium and the lithium base being present in said reaction mixture in amount sufficient to saponify the polymerized 12- hydroxy stearic acid, agitating and heating the mixture of soap and oil to about 250 F. to remove water and elevating the temperature to about 300 to 330 F.

3. A lithium soap grease consisting essentially of a lubricating mineral oil thickened at a maximum temperature of about 300 F. to 330 F. to grease consistency with a soap formed at a temperature of about 170 to 250 F., of a lithium base and polymerized 12-hydroxy stearic acid, the polymerized IZ-hydroxy stearic acid being prepared by heating 12-hydroxy stearic acid to about 150 to 300 F. for a period of time suflicient to reach References Cited in the file of this patent Number UNITED STATES PATENTS Name Date Murphree Jan. 17, 1939 Fraser Apr. 6, 1946 Butcosk Jan. 24, 1950 Whitney Feb. 17, 1953 

3. A LITHIUM SOAP GREASE CONSISTING ESSENTIALLY OF A LUBRICATING MINERAL OIL THICKENED AT A MAXIMUM TEMPERATURE OF ABOUT 300* F. TO 330* F. TO GREASE CONSISTENCY WITH A SOAP FORMED AT A TEMPERATURE OF ABOUT 170* TO 250* F., OF A LITHIUM BASE AND POLYMERIZED 12-HYDROXY STEARIC ACID, THE POLYMERIZED 12-HYDROXY STEARIC ACID BEING PREPARED BY HEATING 12-HYDROXY STEARIC ACID TO ABOUT 150* TO 300* F. FOR A PERIOD OF TIME SUFFICIENT TO REACH SUBSTANTIAL EQUILIBRIUM AND THE LITHIUM BASE PRESENT IN AN AMOUNT SUFFICIENT TO SAPONIFY THE ACID. 